12 x 18 inch silicon carbide shelf in great shape - apart from crack. 1/2 inch thick. previously used in wood fired kiln. Photo is of the bottom of the shelves. Courier cheaper the more you get - the maximum weight with the courier I use is three shelves for $25. Please check out other listings - another single cracked one and about 5 uncracked ones. Being silicon carbide the cracked ones are quite safe to use. Smaller 12 x 12s will be listed soon too - need to photograph first.